Alkylation of aromatic hydrocarbons



Patented st. 30, 1945 ALKYLATION OF AROMATIC HYDRO- CARBONS 7 Raymond E. Schaad, Chicago, IlL, assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application February 11, 1942, Serial No. 430,490

13 Claims.

This invention relates to the treatment of arcmatic hydrocarbons to produce alkylated aromatic hydrocarbons. More specifically it is concerned with the production of mono-alkylated and poly-alkylated aromatic hydrocarbons in the presence of a catalyst.

It is recognized that in general the catalytic alkylation of aromatic hydrocarbons has been known for some time. However, the present in vention difierentiates from the prior art on this subject in the use of a particular catalytic ma-.

terial comprising as its active ingredient a salt or acid salt of an acid of phosphorus and a metal selected from the members of the righthand column of group II of the periodic table, such as an orthoor pyro-acid phosphate of magnesium or zinc.

In one specific embodiment the present invention comprises a process for producing alkylated aromatic hydrocarbons which .comprises subjecting an aromatic hydrocarbon and an olefinic hydrocarbon to contact under alkylating conditions in the presence of a catalyst comprising as its active ingredient a salt of an acid of phosphorus and of a metal selected from the members of the right-hand column of group II of the periodic table and preferably of zinc and magnesium.

Aromatic hydrocarbons, such as benzene, toluene, other alkylated benzenes, napthalene, alkylated naphthalenes, other poly-nuclear aromatics, etc., which are alkylated by olefinic hydrocarbons as hereinafter set forth, may be obtained by the distillation of-coal, by the dehydrogenation of naphthenic hydrocarbons, by the dehydrogenation and cyclization of aliphatic hydrocarbons, alkylated aromatic hydrocarbons, and alkylated naphthenic hydrocarbons, and by other means.

Olefinic hydrocarbons utilizable as alkylating agents in the present instance comprise mono olefins and poly-Olefins. Olefins which are employed in the present process are either normally gaseous or normally liquid and comprise ethylene and its higher homologs, both gaseous and liquid, the latter including various polymers of normally gaseous olefins, but these difierent oleflnic hydrocarbons and those mentioned hereinafter are not necessarily equivalent in their action as alkylating agents. Cyclic olefins may also serve in alkylating aromatic hydrocarbons but generally under conditions of operation different from those employed when alkylating aromatic hydrocarbons by non-cyclic olefins. Other olefinic hydrocarbons which may be interacted with the above indicated aromatic hydrocarbons include conjugated dioleflns such as butadiene and isoprene,

also non-conjugated diolefins, and other polyolefins. Olefinic hydrocarbons utilizable as alkylating agents are obtainable from any source and are present in products of thermal and catalytic cracking of oils, in those obtained by dehydrogenating parafiinic and olefinic hydrocarbons or in the products resulting from dehydrating alcohols.

Alkylation of aromatic compounds may also be effected in the presence of catalysts hereinafter described by charging with the aromatic hydrocarbon a substance capable of producing olefinic hydrocarbons under the operating conditions chosen for the reaction. Such olefin-producing substances include alcohols, ethers, esters, and alkyl halides which are capable of undergoing dehydration or splitting to olefinic hydrocarbons, containing at least 2 carbon atoms per molecule, which may be considered as presentin the reaction mixture even though possibly only as transient intermediate compounds which react further with aromatic hydrocarbons to produce desired reaction products.

Catalysts suitable for use in efl'ecting the process of the present invention comprise salts of acids of phosphorus and metals selected from the members of the right-hand column of group II of the periodic .table consisting of magnesium, zinc, cadmium, and mercury. The preferred catalysts comprise zinc and magnesium phosphates and acid phosphates in which the term phosphate is used in referring to a salt of orthophosphoric acid, tetraphosphoric acid, etc. Metal phosphates utilizable as catalysts and sparingly soluble in water may be formed by adding an aqueous solution of an alkali metal phosphate to an aqueous solution of a group II metal as mentioned above, particularly of magnesium and zinc, to effect precipitation of the desired salt or acid salt which may be separated by filtration from the precipitation mixture, then washed, dried, and used as powdered catalyst or formed into particles suitable for use as a reactor filling material. The metal salts and acid salts utilizable as alkylating catalysts may also be mixed with or deposited upon carriers or supporting materials such as silica, diatomaceous earth, alumina, magnesia, silica-alumina composites, crushed porcelain, firebrick; etc. A composite of a group II metal salt of an acid of phosphorus and a selected carrier in finely powdered form after thorough mechanical mixing, is subjected to drying, Delleting, and heating operations, the latter carried out in a stream of air, nitrogen-hydrogen, or hydrocarbon gases to produce formed particles of cat-,

alyst suitable for use in a reactor employed for effecting alkylation of aromatic hydrocarbons by olefinic hydrocarbons, or the metal salt may itself be similarly formed into pellets or granules usually by compressing a mixture of the powdered catalyst and a suitable pelleting lubricant such as hydrogenated cotton seed oil, starch, etc. The activity of the supported phosphate catalysts is also controlled to a substantial extent by varying the proportions of active salt and carrier. Accordingly catalytic material of appropriate activity is thus available for use with both substantially straight chain olefins and with more reactive olefins. The different alkylating catalysts which may thus be prepared and employed in the present process are not necessarily equivalent in their action.

In effecting reaction between an aromatic hydrocarbon as benzene and an olefin as ethylene, according to the process of the present invention, the exact method of procedure varies with the nature of the reactingconstituents, the activity of the catalyst, the ratio of aromatic to olefinic hydrocarbons, and other factors. A sim-- ple procedure utilizabie' in the case of an aromatic hydrocarbon which is normally liquid, or if solid is readily soluble or easily dispersible in a substantially inert liquid, and a normally gaseous or liquid olefinic hydrocarbon, consists in contacting the aromatic and olefinic hydrocarbons with a catalyst containing a salt or acid salt of an acid of phosphorus and a metal selected from the members of the right-hand column of group II of the periodic table using an alkylating temperature of from about 200 to about 450 C. and preferably from about 250 to about 400 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres. Intimate contact of the reacting components with the catalyst is effected by passing the reaction mixture through a fixed bed of granular or pelleted catalyst or the reactin components may be mixed with finely divided catalyst and reacted in either a batch or continuous type of operation. The hydrocarbons subjected to reaction are preferably in the proportion of 1 molecular proportion of olefinic hydrocarbon to between about 2 and about 20 molecular proportions of aromatic hydrocarbon in order to diminish polymerization of olefinic hydrocarbons and to favor interaction of olefinic hydrocarbons with the aromatic hydrocarbon or mixture of aromatic hydrocarbons in the hydrocarbon fraction undergoing treatment. The addition of a hydrogen-containing gas to the alkylation mixture frequently has a beneficial effect upon the reaction.

Thus a hydrocarbon mixture comprising essentially normally liquid aromatic hydrocarbons and a fraction containing olefinic hydrocarbons are commingled and passed through a reactor containing a salt of an acid of phosphorus as herein described, or at least a portion of the aromatic hydrocarbon is charged to such a reactor while the fraction containing olefinic hydrocarbons, as such or preferably diluted by another portion of the aromatic hydrocarbon being treated, is introduced at various points between the inlet and the outletof the reaction zone in such a way that the reaction mixture being contacted with the catalyst will at all times contain a relatively low proportion of the olefinic hydrocarbon and thus favor interaction of aromatic and olefinic hydrocarbons rather than polymerization of the latter.

While the method of passin the aromatic and olefinic hydrocarbons, either together or countercurrently, through a suitable reactor containing the granular catalyst is generally customary procedure, the interaction of these hydrocarbons may also be effected in a closed vessel in which some of the reacting constituents are in liquid phase and in which the catalyst is preferably in finely divided form and is maintained in dispersion or suspension by some method of agitation. The choice of operating procedure is dependent upon the circumstances such as the temperature, pressure, and activity of catalyst found to be most effective for producing the desired reaction between particular aromatic and olefinic hydrocarbons.

Metal phosphate catalysts as herein described are preferred catalysts as they permit continuous reaction of aromatic and olefinic hydrocarbons in the presence 01' a fixed bed of catalyst and thus make it possible to avoid mechanical problems as well as oxidation and corrosion difliculties encountered when this reaction is carried out in the presence of sulfuric acid which is sometimes used as an alkylating catalyst. Further, a metal salt of a group II metal and an acid of phosphorus has the advantage over aluminum chloride utilized as catalyst for alkylatlng aromatic compounds with olefinic hydrocarbons in that the metal phosphate forms substantiall no addition compounds or complexes with aromatic and/or olefinic hydrocarbons while such formation of addition compounds is characteristic of catalysts containing aluminum chloride.

Reactions between aromatic and olefinic hydrocarbons in the presence of a phosphoric acid salt of a metal of the right-hand column of group II of the periodic table are apparently of a relatively simple character although they may be accompanied by certain amounts of polymerization and decomposition, the latter being particularly in evidence when the reaction is carried out at a temperature in the neighborhood of 450 C. While not understood completely. a typical alkylationcf an aromatic hydrocarbon by an olefin apparently involves the addition of the aromatic hydrocarbon to a double bond of an olefinic hydrocarbon to produce a higher-boiling alkylated aromatic hydrocarbon which may in turn undergo further reaction with one or more molecular proportions of olefinic hydrocarbon to form dialkylated and more-highly alkylated aromatic hydrocarbons. In case the alkylating olefinic hydrocarbon is a diolefin or other poly-olefin, the interaction with an aromatic hydrocarbon may involve not only the combination of aromatic and olefinic hydrocarbons but possibly the polymerization of a higher-boiling unsaturated aromatic hydrocarbon resulting from the primary reaction. Thus benzene and butadiene give among other products a substantial yield of phenyl butenes which polymerize to form dimers of phenyl butene. Within certain limits it is possible to produce mainly mono-alkylated aromatic hydrocarbons by proper adjustment of catalyst activity, ratio of the aromatic to the olefinic hydrocarbons charged, operating conditions such as temperature, pressure, and rate of feed of the reacting components, etc.

Reaction between benzene and ethylene in the presence of the catalysts herein described results in the formation of a relatively high yield of mono-ethyl benzene with a relatively small formation of poly-ethylated benzenes, particularly when the benzene is present in substantial molar excess to the ethylene throughout the entire reaction. The preferred molar ratio of henzene to ethylene is generally between about 4 and 20 although substantial amounts of mono-ethyl benzene are obtained with lesser proportions of benzene in the reaction mixture charged to the process.

The reaction between an aromatic hydrocarbon and a hexene or other normally liquid olefin of higher molecular weight may involve not only addition of aromatic and olefinic hydrocarbons but also a depolymerization or splitting of the olefinic hydrocarbon into olefinic fragments of lower molecular weights which react with the aromatic hydrocarbons to produce alkylated aromatic hydrocarbons. Thu benzene and diisobutene or tri-isobutene react and yield tertiary butyl benzene and poly-tertiary butyl benzenes. while nonene and benzene yield both butyl and amyl benzenes as well as other products by socalled depolyalkylation. 1

In general, the products formed by interaction of an olefinic hydrocarbon with a molal excess of an aromatic hydrocarbon are separated from the unreacted aromatic hydrocarbon by suitable means as by distillation, and the unreacted portion of the aromatic hydrocarbon originally charged and generally the poly-alkylated hydrocarbons formed are returned to the process and mixed with additional quantities of the olefinic and aromatic hydrocarbons being charged to contact with the catalyst. This recycling of polyalkylated aromatic hydrocarbons sometimes aids in the production of mainly mono-alkylated aromatic hydrocarbons and depresses the formation of more-highly alkylated derivatives. The total alkylated product thus freed from the excess of the originally charged aromatic hydrocarbon is separated into desired fractions by distillation at ordinary or reduced pressure or by other suitable means.

The following example is given to illustrate the character of results obtainable by the use of the present process, although the example given is not introduced with the intention of unduly restricting the generally broad scope of the invention.

390 parts by weight of benzene and 42 parts by weight of propene are passed per hour through a reactor containing 100 parts by weight of granular material comprising essentially equal parts by weight of magnesium acid phosphate and diatomaceous earth maintained at a temperature of 350 C. under a pressure of 40 atmospheres. During this treatment 100 parts by weight of alkylated product is formed consisting essentially of mono-isopropyl benzene and relatively small amounts of di-isopropyl benzene.

The nature of the present invention and its commercial utility can be seen from the specification and example given, although neither section is intended to limit its generally broad scope.

I claim as my invention:

1. A process for producing aromatic compounds having a higher number of carbon atoms per molecule than the aromatic compound from which they are derived which comprises subjecting an aromatic compound and an olefinic hydrocarbon to contact under alkylating conditions in the presence of a catalyst containing as its essential catalytically action component an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

2. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an aromatic hydrocarbon and an olefinic hydrocarbon to contact under alkylating conditions in the presence of a catalyst containing as its essential catalytically active component an acid phosphate of a metal selected from the members of the righthand column of group II of the periodic table.

3. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an aromatic hydrocarbon and an olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. in the presence of a catalyst containing as its essential catalytically active component an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

4. A process for producing alkylated aromatic hydrocarbons which comprises subjecting anaromatic hydrocarbon and an olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

5. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an aromatic hydrocarbon and a normally gaseous olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

6. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an arcmatic hydrocarbon and a normally liquid olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the righthand column of group II of the periodic table.

'7. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an arcmatic hydrocarbon and an olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially magnesium acid phosphate.

8. A process for producing alkylated aromatic hydrocarbons which comprises subjecting an aromatic hydrocarbon and an olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially zinc acid phosphate.

9. A process for producing alkylated benzenes which comprises subjecting benzene and a normally gaseous olefinic hydrocarbon to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

10. A process for producing ethylated benzene which comprises subjecting benzene and ethylene to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

'11. A process for producing ethylated benzene which comprises subjecting benzene and ethylene to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially magnesium acid phosphate.

12. A process for producing ethylated benzene which comprises subjecting benzene and ethylene to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst containing zinc acid phosphate as its essential catalytically active component.

13.-A process for producing alkylated benzene which comprises subjecting benzene and propene to contact at a temperature of from about 200 to about 450 C. under a pressure of from substantially atmospheric to approximately 100 atmospheres in the presence of a catalyst comprising essentially an acid phosphate of a metal selected from the members of the right-hand column of group II of the periodic table.

RAYMOND E. SCHAAD. 

